Arbitrum Rollup is the first working rollup implementation to support general solidity contracts, and now we're coming to a Testnet near you. This is the first beta release of Arbitrum as well as the first time we're officially supporting deployment on the Rinkeby.
There have been a massive number of fixes and improvements to our codebase since our last alpha. We have also greatly expanded the amount of documentation available making it easier than ever to get started today.